A100 -- Dan Swearingen
Homework 1 -- Due by the beginning of class on Tuesday September 10:

Part 1. E-mail a message to me. This is to demonstrate
that you have an email account and know how to use email. The email must
come from your own account, not a friend's.

If, and only if, you are a Continuing Education student: you
may satisfy this assignment by writing a complete description (one
you could give your grandparents and they would be able to use it as an
instruction manual) of how an IU student gets an account and uses E-mail.

(2 points) I had to recieve your email message by
class time on September 10.

Part 2. From the text:

(1 point) Page 14 Questions For Review 2:What force holds
the different astronomical systems described in this section together?

Gravity keeps the crust of the Earth, where we live, attached to the
planet. Gravity keeps the planets, comets, and asteroids of the solar system
bound in orbit around the Sun. Gravity keeps the Sun in orbit around the
center of the Milky Way. Gravity keeps the Local Group of galaxies together.

(1 point) Page 14 Questions For Review 3:About how much bigger
in radius is the Sun than the Earth?

The light year (or ly) is defined as the distance light travels in one
year. So if light travels 3 x 105 kilometers each second then
light can travel about 10 trillion kilometers in a year. Therefore a light
year is about 1012 kilometers.

(9 + 9 points) Page 14 Thought Questions and Problems 4:Imagine
building a model of the Solar System on your campus. Work out the diameter
and spacings of the planets in millimeters and meters, respectively (use
1 AU = 1 meter as a scale).

For the planets this means that they are one meter from our model Sun
for every AU they are from the real Sun:

AU

Meters

Feet from sun

Sun

0

0

0

Mercury

0.4

0.4

1

Venus

0.7

0.7

2

Earth

1

1

3

Mars

1.5

1.5

5

Jupiter

5

5

16

Saturn

10

10

33

Uranus

20

20

66

Neptune

30

30

98

Pluto

40

40

131

For the sizes of the planets we must first calculate how much smaller
the model solar system is than the real solar system.

This gives us:

R in km

R in Model (km)

R in mm

Sun

700,000

4.67E-06

5

Mercury

2,439

1.63E-08

0.02

Venus

6,051

4.03E-08

0.04

Earth

6,378

4.25E-08

0.04

Mars

3,397

2.26E-08

0.02

Jupiter

71,492

4.77E-07

0.5

Saturn

60,268

4.02E-07

0.4

Uranus

25,559

1.70E-07

0.2

Neptune

24,764

1.65E-07

0.2

Pluto

1,123

7.49E-09

0.01

The point here is that on this scale where we have pluto 130 feet from
the Sun, all the planets are too small to draw except for the gas giants
(which are dots!).